Grille structure for television picture tubes



Oct. 14, 1958 H. J. EVANS 2,855,552

GRILLE STRUCTURE FOR TELEVISION PICTURE TUBES Filed March 15, 1956 aSheets-Sheet 1 lNVENTOR HOWARD J. EVANS, BY 7 HIS ATTORNEY.

GRILLE STRUCTURE FOR TELEVISION PICTURE TUBES Filed March 15, 1956 5Sheets-s eet 2 HIIIH|| r I. 14H WWW W W A J Jlllllldillih- HOWARD J.EVANS,

HIS A NE Oct. 14, 1958 H. J. EVANS 2,856,552

GRILLE STRUCTURE FOR TELEVISION PICTURE TUBES Filed March 15, 1956 5Sheets-Sheet 3 FlG.4

' 57 i3: I l

HIS ATT RNE GRHLLE STRUCTURE FOR TELEVISION PICTURE TUBES Howard J.Evans, Fayetteville, N. Y., assignor to General Eieetric Company, acorporation of New York Application March 15, 1956, Serial No. 571,769 9Claims. (Cl. 313-85) The present invention relates to television picturetubes of the post acceleration type and more particularly to new andnovel means for positioning grille structures in post accelerationtubes.

Certain color television picture tubes of the post acceleration typeinclude an image reproducing structure including a viewing screen havinga plurality of triplets of luminescent elements disposed inpredetermined arrangement thereon and adapted to be impinged upon byelectron beams, and a grille structure or apertured mask interposedbetween a source of electron beams and the viewing screen. The grillestructure or apertured mask serves as a lens means to focus the electronbeams onto :the luminescent elements.

Because of various factors relating to the better opera- :tion of postacceleration type color television picture :tubes, an embodiment of thistype tube has been selected 'which employs a screen composed of aplurality of tripilets of luminescent stripes disposed in verticalorientation,

and having a grille structure composed of a plurality of wires inparallel relation to each other and substantially parallel to the screenand aligned with the luminescent stripes thereon.

For proper operation of post acceleration tubes the grille structuremust be positioned accurately at a predetermined distance from thescreen of the picture tube. Further, each of the wires of the grillestructure must be aligned with respect to the luminescent stripes inorder that electron beams modulated by a given color signal impinge onthe corresponding color producing luminescent elements. Misalignment ofthe grill structure with relation to luminescent elements, or improperdistance positioning of the grille with relation to the screen restiltsin color impurities.

Accordingly, it is a principal object of the present invention toprovide a new and novel support structure for accurately positioning andmaintaining the position of the grille structure of post accelerationtype color television tubes.

it can be appreciated that because vertical stripes are used in thisselected embodiment of the post acceleration tubes, close alignmentbetween the grille and the screen in the vertical direction is notessential. Small errors in the vertical direction can be tolerated,inasmuch as a small vertical variation of the point at which the beamimpinges will not result in any color impurity. However, alignment inthe horizontal direction is still critical since each of the luminescentstripes is approximately 0.012 inch in width and the electron beam spotis approximately 0.006 inch wide. The beams should normally impinge atthe center of each stripe; an error of more than three mils will showsome degree of color impurity.

it is therefore another object of the present invention to provide a newand novel structure for aligning the grille wires With the luminescentstripes.

Further, the grille wires must be maintained in position even though thetube containing the grille wires therenite States atent O f PatentedOct. 14, lQEiiZ-r within is subjected to shocks and vibrations due to,for example, handling and the shipping operations required to place atelevision set incorporating said tube in the customers home.

It is therefore yet another object of the invention to provide a novelsupport for the grille structure of a post acceleration type tube whichis resistive to shock and vibration forces.

It has been found advantageous for reasons of economy and strength tomanufacture face panels for picture tubes having a curved viewing areawhich has a radius of curvature along a vertical axis perpendicular tothe horizontal axis of tube and a second radius of curvature along anaxis normal to the vertical axis. The curvature around a vertical axis,for example, in one embodiment of a rectangular shaped 22 inch picturetube has a radius of about 33 inches. The aforementioned viewing areaalso has a second but a more slight radius of about 250 inches in adirection normal to the vertical axis.

Another advantage of a curve face panel is that positioning of thegrille structure with respect to the face panel becomes less criticaldue the curvature of the face panel, as will be explained hereinbelow.Various configurations have heretofore been attempted to accurately,etficiently, and economically position and align the grille structurewith relation to the face panel. All the previous solutions havelimitations in one or more of the above respects.

In the luminescent stripe arrangement employed in the present tube anerror in the horizontal direction causes color impurity while an errorin the vertical direction does not have serious deleterious effects oncolor purity. As is well known, six constraints are required tocompletely determine a solid body. Since small displacements parallel tothe luminescent stripes can be tolerated in the embodiment of myinvention, only five constraints are required to be accurately fixedwhen positioning the grille structure with relation to the luminescentstripes. Rigidity and accuracy normal to the luminescent stripes isemphasized. The constrainting forces are disposed such that all saidforce vectors are either parallel or normal to the luminescent stripesand each of said force vectors have no components in an orthogonaldirection.

One embodiment of the prior art of which I am aware employs a threepoint support provided on the face panel for corresponding engagingpoints on a frame member. The three supports are disposed more or lesssymmetrically around the frame member. If for example a rectangularframe is employed, one support is disposed at the center of one side ofthe rectangle and the other two points are on the opposite side of therectangular frame. it can be appreciated that if this prior art frame isto be aligned with the face panel, all three points of the frame membermust be perfectly aligned with the three points of the face panel. Thethree point system of the prior art depends for alignment on constraintswhich are actually at rather large angles, of about 30, with theluminescent stripes due to the triangular geometry of the support. Eachof such constraints have components of force in a direction parallel tothe stripes as well as components normal to the stripes, andconsequently have to be accurately positioned in both directions,needlessly adding one extra position which has to be accuratelydetermined. Thus, such a three point sys tem is more critical to alignsince an error of alignment in either direction may result in colorimpurity. Further, in said three point support system no means arereadily available for correcting the alignment of the frame withrelation to the viewing area nor for readily adjusting the distancespacing between the frame and the viewing area.

It is therefore yet another object of the invention to provide a novelmeans for positioning and supporting the grille structure in a tubehaving a curved viewing area.

Further objects and advantages of my invention will become apparent fromthe following description and the features of novelty which characterizemy invention willbe pointed out with particularity in the claims annexedto and forming part of this specification.

In carrying out the objects of my invention, 1 provide a novel facepanel structure for a picture tube, said face panel having a curvedviewing area and providing a two location support for a grillestructure, said structure being constrained by screw means affixed tothe face panel to conform substantially to the shape of the viewing areasurface.

For a detailed explanation of my invention, reference is made to theaccompanying drawings in which:

Figure l is an elevation view, partly in cross section of' a picturetube constructed in accordance with one embodiment of my invention;

Figure 2 is an enlarged plan view taken along the line 22' of Figure 1;

Figure 3 is a cross sectional side view taken along the line 33 ofFigure 2;

' Figure 4a is an enlarged isometric view partly in cross section of theland member of the preceding figures;

' Figure 4b is a side view partly in cross section of the land structureof the preceding figures;

Figure 5 is a front view partly in cross section of the land structureof Figure 4b;

' Figure 6 is an enlarged cross sectional side view of the aligningscrew structure of Figure 3; and

Figure 7 is another embodiment of the aligning screw structure of Figure6.

In Figure 1, a color television picture tube 11 of the post accelerationtype is shown including a cone or funnel portion 13, a face panel member15 having disposed in the inner face thereof a viewing area 17consisting of a screen of a luminescent material including a conductivecoating thereon, and flange members 19 and 21 for joining panel 15 tocone 13. Tube 11 further includes a grille structure including a wiregrille pattern 21, and a frame member 23 disposed adjacent screen 17.Beam forming means 25 located in the neck portion 27 of tube 11 providea source of electron beams which are suitably deflected by yoke 29.Connectors 31 couple the tube to suitable energy providing means. Asource of voltage, not shown, is coupled between grille 2t? and screen17 to. provide an electron beam accelerating potential therebetween.

\ Figure 2 is a plan view of the face panel along line 22 of Figure 1.The grille pattern 21 consists of a plurality of spaced parallel wiresafixed to the lower side of the frame 23. The wires 21 are affixed tothe lower side of frame 23 so that there be no metallic elements betweenthe frame 23 and the viewing area 17.

The wires are affixed to frame 23 prior to inserting the structure intothe face panel 15.

When the wires are aflixed to the frame member there is a slightcompression of the frame which is compensated for by pro-stressing theframe. if this pre-stressing is correct, there will be no deformation ofthe frame from an initially predetermined form when the load is shiftedfrom the pre-stressing rods to the grille wires.

Figure 3 is a side view partly in cross section aiong lines 33 of Figure2. it can be seen in Figure 3 viewing area 17 of the face panel 15 has acurvature along a vertical axis perpendicular to the axis of the tube.

The fact that the viewing area is curved makes positioning and aligningof the grille structure 20 a less complex problem than it would be thecase in a tube employing a flat viewing area.

Assuming a straight face panel perpendicular to the tube axis, it can beappreciated that as a distance on the face panel between the point wherethe tube axis intersects the face panel and the point at which a beamimpinges increases, the more critical the positioning becomes. A beamimpinging on the face panel a large distance from the tube axis has alarge component of velocity parallel to the face panel and therefore asmall error in positioning will cause a relatively large variation ofthe point at which the electron beam impinges due to the component ofvelocity parallel to the face panel. If the face panel is curved thenthe entire surface of the face panel on which the electron beamsimpinges is more nearly the same distance from the source of theelectron beams, and all surfaces are more nearly perpendicular to theelectron beams. Any error in positioning is thus less accented by errorsdue to electron beam velocity components parallel to the face panelsurface as is the case for a flat VICWlng 21163.

The grille structure 20 must be positioned at a predetermined distancefrom the phosphor screen throughout the entire area of the grille wires21. Lands 34 and 35 are molded into the face on the mid-point of thelong sides of the rectangular sides of the face panel. An isometric viewof one land 35 is shown in Figure 4a. The lands have a cylindrical boss37 whose axis is parallel to the wires in the grille. A portion of theland 35 is precision ground to obtain a fiat surface 39 to determine theexact distance of the wires from the phosphor surface. The frame 23rests on the surface 39; but the wires 21 are alfixed to the frame suchthat the wires do not rest on surface 39, Figure 4b. An L. shaped tabmember 41 having a lateral adjustment screw 43 is affixed to the frame23 by a pair of screws 45 at the mid-point of the long side of the frame23, as shown in detail in Figure 5.

The grille wires 21 may conveniently be aligned with the luminescentstripes by employing a mask member (not shown) cut in the shape of theviewing area 17 and having six apertures cut in spaced parallel positionon the surface thereof. Two of the apertures in the mask are in verticalalignment with the axis of the tube. A pair of apertures in verticalalignment with each other are cut to either side of the aperturesaligned with the axis. The mask member is placed in predeterminedposition between a light source and the viewing area 17. The aperturesadmit light to impinge on the grille and produce shadows on theluminescent stripes to which shadow point particular grille wires shouldbe aligned. Thus, the grille structure is adjusted such that threesymmetrically spaced groups of wires are aligned at each end with thestripes on the viewing area at predetermined points. Any errors in theviewing area of the face panel and also any errors in the grillestructure generally vary in a smooth and not in an abrupt manner. Thus,if alignment is made for three symmetrically spaced groups of parallelgrille wires with relation to the viewing area, corrective alignment ofthe entire grille structure with the relation to the viewing area isreadily obtained.

An alternating method of positioning the grille wires with relation tothe luminescent stripes may be employed. If in laying down the grillewires onto the frame, the lathe jig (not shown) on which the grilleframe may be wound has cylindrical indexing bosses similar to the bosseson the face panel as reference positions for winding the wires, then theframes become interchangeable provided the printing is referenced withrespect to the bosses on the face panel. The advantages of this methodare interchangeability of frames, with consequent economy and speed ofproduction.

As shown in Figure 5, a tab 47 having a trapezoidal cutout 49 is placedsecurely over surface 37 and is welded to tab 41. Because of therespective geometries of the surface 37 and the cutout 49 the cutoutportion bears against the land 35 along two points 51 and 52 to preventany lateral motion of the grille structure 23.

The lateral adjustment screw 43 bears against a surface 44 on the sideof the face. panel 15 to avoid translation c t mr n a neme s t the ePreferably the surface 44 is perpendicular to the axis of screw 43. Theend of the lateral screw 43 has a ballshaped nose so that the force onthe frame 23 is transmitted solely along the axis of the screw.

Land structures34 and 35 are similar and the frame is aiiixed to bothland structures in the same manner. Therefore, only land structure 35 isdescribed in detail.

For quantity production it is important that the assembly use a minimumamount of jigs for positioning the grille at the predetermined distancefrom the screen and that positioning be rapid and relatively free fromany complications. In the present embodiments, precision screws bearagainst face panel supports to position the frame and may be readilyadjusted and locked in place as will be presently discussed.

Frame 23 is initially fabricated to have a radius as shown by the solidlines, Figure 3. .The frame 23 is made to a smaller radius than is theface panel 15, taking into consideration also any tolerance variationswhich the face panel may have. In the embodiment of the invention, theframe is overdetermined, so to speak, by the multiplicity of constraintsemployed, and the additional constraints are advantageously employed tobend or force the frame to conform substantially to the viewing area ofthe face panel. As is well known, a solid body requires threeconstraints to determine its translation and three more constraints todetermine its rotation. In the embodiment of my invention there are nineconstraints, one constraint each at the two points where the trapezoidcontacts the boss on each of the lands, one constraint provided by thelateral screws, and one constraint on each of the four corners.Therefore, three constraints are available to provide deformations ofthe frame to conform said frame to the viewing area as well as forcorrections of malformations in manufacture or processing of either orboth the viewing area and the grille structure.

After the frame 23 is secured with references to the lands 34 and 35,the distance adjustment screws 53, 55, 57 and 59 are inserted in theopen end apertures of protrusions 54, 56, 58 and 60 respectively, of theflange 19. Each of the four distance adjustment screws and each of thefour protrusions are similar so that only one will be described.

'In Figure 6, the distance adjustment screw includes a female portion 62having ball-shaped nose 61 which engages the frame member 23 in anoversized recess 63; thus, the screw 59 exerts pressure against theframe 23 only in a downward direction. The female portion 62 threads tothe male portion 65 which includes shoulder 67 which bears againstprotrusions 60 of flange member 19. From Figure 2 it can be seen thatthe screw 59 can be easily slipped in on the side of protrusion 60 andis maintained in position while tightening by spring clips 72 welded tothe protrusions. Each of the protrusions has spring clips although onlytwo clips 70 and 72 are shown in the drawing.

The correct distance from the luminescent screen having been determined,screw 59 is adjusted until the frame is brought to predeterminedposition, for example, at a position indicated by dot-dash line 23'(Figure 3). After adjustment, screw 59 may be locked into place by anut, not shown, or by brazing the screw at the point at which the twoportions join.

After the four screws 53, 55, 57 and 59 are adjusted, the frame 23 isnow at a correct distance from the phosphor screen at six points.Because of the variation of the frame from the correct distance betweenthese six reference points tend to be smooth rather than abrupt, a veryclose approximation to the exact spacing distance between the screen 17and the frame 23 will be attained all along the frame 23.

Figure 7 shows another embodiment of the invention. A small glassprotrusion 69 may be molded and shaped to have a downward L-shapedextension with a substantial- 1y round end The female portion 62 ofscrew 59' is similar to that of the embodiment of Figure 6. The maleportion 65' includes an oversized flange having a round recess 64 on thetop which engages the round end of the protrusion 69. Thus, no flangeprotrusion is needed to provide positioning and securing means for frame23. A principal advantage of this embodimentis that a minimum ofmetallic parts extend toward the viewing area and no metal flange isrequired for closure of the face panel and the cone.

Although the description has been directed primarily to curved surfaces,it will be understood that either or both of the radii of the viewingarea may be infinite, or in other Words, forming cylindrical or flatsurfaces or surfaces of any desired curvatures.

While specific examples have been given in describing details of thisinvention, it will be understood that they have been given merely by wayof illustration and thatthe invention is not limited thereto.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. In combination, a face panel for a television picture tube having aviewing area, a grille structure adapted to be disposed adjacent saidviewing area, said grille member including a frame member configured tobound said viewing area, a first and second supporting means engageablewith said frame respectively disposed upon said panel at diametricallyopposed bounds of said viewing area and arranged to partially define theposition of said frame with respect to said panel when said frame isheld in engagement therewith by pressure perpendicular to said panel,and a plurality of additional supporting means also disposed along saidbounds and disposed respectively to one side and to the other of saidfirst two recited supporting means arranged to press perpendicularly tosaid panel to hold said frame into engagement: with said first tworecited supporting means for positioning said grille on said panel. It

2. In the combination set forth in claim 1 wherein said first tworecited supporting means, when engaging said frame, are arranged toconstrain said frame to permit freedom of motion thereof only inrotation about and translation along a line between said first tworecited supporting means.

3. In the combination set forth in claim 1 wherein said first tworecited supporting means, when engaging said frame, are arranged toconstrain said frame to permit freedom of motion thereof only inrotation about a line between said first two recited supporting means.

4. In the combination as set forth in claim 1 wherein said first tworecited supporting means, when engaging said frame, are arranged toconstrain said frame to perrnit freedom of motion thereof only inrotation about a line between said first two recited supporting means,and said additional supporting means, while constraining said frame in adirection perpendicular to said panel to prevent. said rotation, exertrelatively no constraint upon said frame in a plane parallel to saidpanel.

5. In combination, a face panel for a television picture tube having aviewing area, a grille structure adapted tobe disposed adjacent saidviewing area, said grille member including a deformable frame memberconfigured to bound said viewing area, said frame member having a.natural radius of curvature dissimilar from that ulti-- mately desired,a first and second supporting means en-- gageable with said framerespectively disposed upon said. panel at diametrically opposed boundsof said viewing:

area and arranged to partially define the position of said.

frame permitting freedom of motion thereof only in rota-- tion along aline between said supporting means when said frame is held in engagementtherewith by pressure perpendicular to said panel, and a plurality ofadditional adjustable supporting means also disposed along said boundsand disposed respectively to one side and to the other of said first tworecited supporting means, arranged to press perpendicularly to saidpanel to hold said frame into engagement with said first two recitedsupporting means to completely determine the position of said frame Ically curved grille structure adapted to be disposed adjacent saidviewing area, said grille member including a deformable frame memberconfigured to bound said viewing area, said frame member having anatural radius. of curvature smaller than that ultimately desired, afirst and second supporting means engageable with said framerespectively disposed upon said panel at diametrically opposed bounds ofsaid viewingv area and arranged to partially define the position of saidframe at-a predetermined distance with respect to said panel when said.frame is pressed toward said panel into engagement with said supportingmeans, and a plurality of additional adjustable supporting means alsoarranged along said bounds and disposed respectively to one side and tothe other of said first two recited supporting means, arranged to exerta force towards said panel upon said frame to completely determine theposition of said frame and to deform said frame into the desiredcurvature.

7. A color television picture tube comprising a substantiallyrectangular cup-shaped face panel including a curvedviewing areathereon, a flange member affixed to the open ends of said face panel, agrille structure disposed adjacent said curved viewing area, said grillestructure comprising an initially curved frame member of a smallerradius than saidface panel, a grille wire pattern affixed to said framemember, support means for said frame member disposed in the center oftWo opposite sides of said rectangular face panel, said support meanscomprising a raised land having a flat surface thereon, saidlandincluding a rounded boss, a tab member affixed tosaid frame, asecond tab member having a trapezoidal cutout portion, said portionbeing adapted to bear against said boss, said first tab affixed to saidsecond tab for determining translation of said frame in a lateraldirection, said frame having bowl-shaped depressions disposed on thefour corners thereof, screw members adapted to engage said frame at eachof said depressions to exert a force parallel to the axis of said screwbetween said flange member and said frame member to constrain said framemember to conform substantially to the surface of said viewing area at apredetermined distance from said viewing area, means afiixed to saidfirst tab bearing against the sides of said face panel to determinetranslation of said frame in a direction normal to said lateraldirection.

8. A color television picture tube comprising a face panel including acurved viewing area thereon, a grille 8, structure disposed adjacentsaid curved viewing area, said grille structure comprising an initiallycurved frame member of a smaller radius than said face panel, a grillewire pattern affixed'to said frame member, support means for said framemember disposed in the center of opposite sides of said'face panel, saidsupport means comprising a raised land having-a fiat surface thereon,said land including acylindrical boss, a tab member affixed to saidframe, a second tab memberhaving a trapezoidal cutout portion bearingagainst said boss, said first tab affixed to said second tab fordetermining translation of said frame in a lateral direction, anextension formed on the sides of said face panel, saidframe havingbowlshaped depressions disposed on the four corners, thereof, screwmembers adapted to engage said frame at each of said depressions toexert a force along the axis of said screw between said extensions andsaid frame'rnember to constrain said frame member to conformsubstantially to the surface of said viewing area at a predetermineddistance from said viewing area, means affixed to said first tab bearingagainst the sides of said face panel to determine translation of saidframe in a direction normal to said lateral direction. 9. A colortelevision picture tube comprising a face' panel including a curvedviewing area thereon, a grille structure disposedadjacent said curvedviewing area, said grille structure comprising an initially curved framemem ber of a smaller radius than said face panel, a grille wire patternaffixed to'said framemember, support means for said frame memberdisposed in the center of opposite sides of said facepanel, said supportmeans comprisinga raised land having a flat surface thereon, said landincluding a cylindrical boss, a tab member aflixed to said frame, asecond tabmember, having a trapezoidal cutout portion bearing againstsaid boss, said first tab afiixed to said secondtab for determiningtranslation of said frame in a lateral direction, an Leshaped extensionformed on the.

sides of said face panel screw members positioned to exert forcesbetween. said flange member and said frame member such that said framemember is constrained to conform substantially to the surface of saidviewing area at a predetermined distance from said viewing area, meansaflixed to said first tab bearing against the sides of said face panelto prevent translation of said frame in a direction normal to saidlateral translation.

ReferencesCited-in the file of this patent UNITED STATES PATENTS LawJan. 20, 1953 2,683,833 Zaphiropoulos July 13, 1954 2,727,172 Mark Dec.13, 1955 2,755,405 Wilhelm July 17, 1956

